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Finite groups with more than two pairwise inequivalent doubly transitive representations all with the same permutation character were studied originally by Wielandt and Ito. Recently Cameron  has… (More)
AbstractIt is shown that ifA is an orthogonal array (N, n, q, 3) achieving Rao's bound, thenA is either(i)an orthogonal array (2n, n, 2, 3) withn ≡ 0 (mod 4), or(ii)an orthogonal array (q3,q + 2,q,… (More)
We give some inequalities for Steiner systems S(t,k,v) which improve the inequalityv? (t+ l)(k?t+l) and Fisher's inequalityv?t+l?(k?t+l)(k?t+2).
The following theorem is proved.Theorem. An inequalityv ≧ (t + 1)(k −t + 1) + (k −t) holds for Steiner systemsS(t, k, v) witht < k < v andt even with equality if and only if (t, k, v) = (t, t + 1, 2t… (More)
On considere les graphes fortement reguliers qui peuvent se partager en deux sous graphes fortement reguliers avec un nombre egal de sommets